This invention relates to fetal monitoring devices and more specifically to an improved interface apparatus adapted to better position electronic transducers on women during labor.
Practitioners and hospitals routinely use continual or periodic fetal monitoring during labor. Fetal monitoring is also performed on the patient during some prenatal consultations. This enables the practitioner to assess the condition of the fetus during antepartum, labor and delivery.
Electronic fetal monitoring (EFM), a preferred technique of fetal monitoring, uses an electronic monitoring and recording machine to process signals transmitted from sensors or transducers positioned on the patient. For example, during labor, the EFM system continuously monitors and records the fetal heart rate (FHR) and uterine contractions. The transducers connect either by wireless telemetry or by a hard-wired cable directly to the recording and monitoring machine. Examples of fetal monitoring machines include, but are not limited to, the system described in U.S. Pat. No. 4,781,200 to Baker issued on 01 Nov. 1988. Another example of a fetal monitoring machine is brand Corometrics 250-series model number 0172WAT-B manufactured by GE Healthcare Technologies of Waukesha, Wis. USA. Other machines made by Hewlett-Packard, for example, are also contemplated.
Electronic fetal monitor devices automatically and continuously monitor and record the heart rate of the fetus to assist practitioners in assessing the well-being and status of the fetus. Electronic fetal monitors include one or more fetal cardiac sensors including acoustic, electro-cardiographic, or bioimpedence type sensors. The electronic fetal monitor device converts sensor signals into digital signals for processing and recording. Recording includes printing a time-based paper record of the parameters measured along with a computer-generated reading stored on a disk and hard drive.
Non-invasive, external fetal monitoring techniques are most commonly employed during labor and delivery. This non-invasive technique incorporates ultrasonic waves to reflect off the fetal heart and are sensed by an appropriate sensor and process to determine the frequency shift associated with the reflection from the moving fetal heart valve according to the Doppler Principle.
This ultra-sonic, non-invasive technique crucially relies on the proper placement Including location and direction or angle of the external sensor or transducers on the patient. The two disk-like electronic transducers position on the patient's abdomen and are held in place by wider, stretch bands that circle the entire torso. The stretch bands, also termed a sensor belt, include one or more pieces of flexible, expandable material adapted to accommodate the curves of the maternal midsection during the later stages of pregnancy. Typically, the belt pieces adapt to extend over portions of the patient's abdomen and are made from a stretchable material, such as the type sold under the trade name Lycra or Spandex. A type of hook-and-loop closure, such as Velcro-brand fastener, enables opposing ends of the belt to releasably and selectively couple together. And, the belt feeds through two opposing slots arranged on either side of the transducer. An example of an ultrasound transducer holder is described in U.S. Pat. No. 4,920,966 to Hon et al. issued on 1 May, 1990.
To obtain accurate readings of both the FHR and uterine contractions, each respective transducer must be appropriately aligned and positioned on the patient's abdomen. This alignment requires practiced skill because to record the FHR, not only must the transducer be properly located on the abdomen of the patient, it must be simultaneously directed toward the heart valve of the fetus. Additionally, the strap or belt members used to retain the transducer must be both snug enough to maintain proper alignment of the transducer, yet be comfortable to the laboring patient.
A misalignment of the transducer will prevent accurate readings, send false readings, or not register readings. Once properly placed the transducer is continually exposed to erratic movements of the patient and position changes, movements, and descent of the fetus. And, even moderate movement of the patient or fetus can result in erroneous readings.
To maintain useful readings from the transducers, the practitioner must frequently re-position the transducer. This often requires considerable effort by the practitioner. Sometimes, the practitioner must manually hold the transducer in place to record the FHR for a period of time. Alternatively, in some instances the patient must remain in one position for a set period of time to allow a recording of the FHR. These approaches are often not feasible and the only alternative is to utilize an invasive form of fetal monitoring. One common invasive technique teaches placing an electrode on the fetal scalp. When a fetal scalp electrode is contra-indicated due to the patient's medical condition or fetal presentation, and the practitioner cannot remain at the patient's bedside to manually hold the transducer in the exact position, the patient may be required to stay in one position throughout the labor to facilitate adequate monitoring of the fetus; however, labor dystocia can occur, thus necessitating a cesarean section.
Therefore, there is a need for an improved fetal monitoring transducer mounting system and apparatus that enables a practitioner to more precisely change and maintain the angle of an ultrasonic transducer. Further, such a system and apparatus should readily adapt to existing transducers already being used by practitioners in clinics and hospital delivery rooms.